Patent Application
20080204325
1. Field of the Invention
The present invention generally relates to an antenna apparatus, and more particularly relates to a planar antenna apparatus using UltraWideBand (UWB).
2. Description of the Related Art
In recent years, wireless communication technologies using UltraWideBand (UWB) have gotten a lot of attention because of UWB's wide range of applications such as radar positioning and high capacity transmission. In 2002, the Federal Communications Commission (FCC) of the United States approved the use of UWB in the frequency band between 3.1 and 10.6 GHz.
UWB is a transmission system using ultrawideband signals for communication. An antenna used for UWB must be capable of sending/receiving ultrawideband signals.
An antenna, which is composed of a base board and a power feeder, for use in the frequency band between 3.1 and 10.6 GHz approved by FCC has been proposed (non-patent document 1).
An antenna apparatus 20 shown in
[Non-patent document 1] 2003 IEICE (The Institute of Electronics, Information and Communication Engineers) General Conference, Mar. 22, 2003, Room B201, B-1-133: An Omnidirectional and Low-VSWR Antenna for the FCC-Approved UWB Frequency Band, Takuya Taniguchi and Takehiko Kobayashi (Tokyo Denki University)
[Patent document 1] Japanese Patent Application Publication No. 2000-196327
As described above, a conventional wide-band antenna apparatus normally has a structure where a cone-shaped or teardrop-shaped power feeder is placed on a base board. Because of this structure, a conventional wide-band antenna apparatus is normally large in size, and therefore there has been demand for a more compact and thinner antenna apparatus.
The ground patterns 34 and 35 form ground potential regions near the antenna element pattern 32 and thereby generate lines of electric force around the antenna element pattern 32. Also, the ground patterns 34 and 35 constitute a part of a microwave transmission line 40 of a Coplanar waveguide type.
The stripline 33, the ground patterns 34 and 35, and the base 31 form the microwave transmission line 40 of a Coplanar waveguide type. The coaxial connector 40 is soldered onto the stripline 33 and the ground patterns 34 and 35 at the end of the microwave transmission line 40 of a Coplanar waveguide type extending from the antenna element pattern 32.
The planar UWB antenna apparatus 30 is used in the frequency band between 3 and 6 GHz.
The line Ia in
The present invention provides an antenna apparatus that substantially obviates one or more problems caused by the limitations and disadvantages of the related art.
According to an embodiment of the present invention, an antenna apparatus includes a base made of a dielectric material; an antenna element pattern formed on a surface of the base; a ground pattern formed in a position adjacent to and opposite to the antenna element pattern on the same surface of the base; and a surface-mounted coaxial connector mounted on the ground pattern in a position close to a feeding point of the antenna element pattern.
c are drawings illustrating an exemplary socket coaxial connector;
Preferred embodiments of the present invention are described below with reference to the accompanying drawings.
The planar UWB antenna apparatus 100 includes an antenna element pattern 102, a short stripline 103 with a length of about 1 mm, and a ground pattern 104 formed on an upper surface 101a of a base 101 made of a dielectric material. Also, a surface-mounted socket coaxial connector 200 is placed in a position close to a projecting point (feeding point) 102a of the antenna element pattern 102 so as to span a gap between the end of the stripline 103 and the ground pattern 104.
As shown in
The stripline 103, a part of the ground pattern 104 which part faces the stripline 103, and the base 101 form a microwave transmission line 110 of a Coplanar waveguide type. The microwave transmission line 110 has an impedance of about 50Ω.
The ground pattern 104 forms ground potential regions near the antenna element pattern 102 and thereby generates lines of electric force around the antenna element pattern 102.
A land 120 is formed on the edge of the stripline 103 and a land 121 is formed on an area surrounding the recess 104a of the ground pattern 104. The socket coaxial connector 200 is mounted on the lands 120 and 121.
As shown in
The shielding unit 200a is made of a conductive material and includes a connecting part 200d and contacts 200e1, 200e2, and 200e3. The connecting part 200d is shaped like a cylinder, protrudes in the Z1 direction, and engages a shield of a plug connector. The contacts 200e1, 200e2, and 200e3 are connected to the connecting part 200d and exposed on the bottom surface of the insulating part 200c (the surface in the Z2 direction).
The signal line connecting unit 200b is made of a conductive material and includes a connecting pin 200f and a contact 200g. The connecting pin 200f is positioned within the connecting part 200d, protrudes from the insulating part 200c in the Z1 direction, and is connected to a signal line of the plug connector when the plug connector is inserted. The contact 200g is connected to the connecting pin 200f and exposed on the bottom surface of the insulating part 200c (the surface in the Z2 direction).
The socket coaxial connector 200 is surface-mounted by soldering the contact 200g onto the land 120 on the edge of the stripline 103 and soldering the contacts 200e1 and 200e2 onto the land 121 on the ground pattern 104.
Since the microwave transmission line 110 is a Coplanar waveguide type, a line width s of the stripline 103 is as large as 1 mm as shown in
The planar UWB antenna apparatus 100 is usable in the frequency band between 3 and 6 GHz and is used by connecting a plug coaxial connector (not shown) attached to one end of a coaxial cable (not shown) to the socket coaxial connector 200. A high-frequency signal is supplied to the antenna element pattern 102 and the ground pattern 104 is held at ground potential. As a result, lines of electric force are generated between the antenna element pattern 102 and the ground pattern 104.
In
The VSWR vs. frequency characteristics of the planar UWB antenna apparatus 100 and the planar UWB antenna apparatus 30 shown in
At around 3 GHz, the VSWR of the planar UWB antenna apparatus 100 is about 1.4 and is about a half of the VSWR of the planar UWB antenna apparatus 30.
At around 4 GHz, the VSWR of the planar UWB antenna apparatus 100 is about 1.1 and is substantially the same as the VSWR of the planar UWB antenna apparatus 30.
At around 5 GHz, the VSWR of the planar UWB antenna apparatus 100 is about 1.5 and is about 0.2 lower than the VSWR of the planar UWB antenna apparatus 30.
At around 6 GHz, the VSWR of the planar UWB antenna apparatus 100 is substantially the same as the VSWR of the planar UWB antenna apparatus 30.
The above results show that, in the frequency band between 3 and 6 GHz where the planar UWB antenna apparatuses are used, the VSWR vs. frequency characteristics of the planar UWB antenna apparatus 100 are better than the VSWR vs. frequency characteristics of the planar UWB antenna apparatus 30.
Possible reasons of the above improvement in VSWR vs. frequency characteristics are as follows:
(1) The planar UWB antenna apparatus 100 includes only one ground pattern, the ground pattern 104. Because of this structure, a half of the ground pattern 104 corresponding to the X1 side of the antenna element pattern 102 and the other half of the ground pattern 104 corresponding to the X2 side of the antenna element pattern 102 show the same ground potential.
(2) The socket coaxial connector 200 is mounted on the ground pattern 104 in a position close to the antenna element pattern 102. Because of this structure, the ground potential of the half of the ground pattern 104 corresponding to the X2 side of the antenna element pattern 102 becomes stable.
Unlike the planar UWB antenna apparatus 100, the planar UWB antenna apparatus 100A does not have a microwave transmission line of a Coplanar waveguide type. In the planar UWB antenna apparatus 10A, the socket coaxial connector 200 is soldered onto the land 120 formed on the feeding point 102a of the antenna element pattern 102 and onto the land 121 formed on a part of the ground pattern 104 which part faces the feeding point 102a so as to span a gap between the antenna element pattern 102 and the ground pattern 104. The contact 200g of the socket coaxial connector 200 is soldered directly onto the feeding point 102a of the antenna element pattern 102.
The planar UWB antenna apparatus 100A shows substantially the same VSWR vs. frequency characteristics as those indicated by the line I shown in
A planar UWB antenna apparatus according to an embodiment of the present invention includes an antenna element pattern, one ground pattern, and a surface-mounted coaxial connector mounted on the ground pattern in a position close to a feeding point of the antenna element pattern. Such a configuration stabilizes the ground potential of the ground pattern and thereby improves the VSWR vs. frequency characteristics of a planar UWB antenna apparatus.
The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention.
The present application is based on Japanese Priority Application No. 2006-094459 filed on Mar. 30, 2006, the entire contents of which are hereby incorporated by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-094459 | Mar 2006 | JP | national |
